The relationship between endogenous gibberellins and rosetting in Eustoma grandiflorum

Abstract

Treatments with gibberellin A1 (GA1), GA3 and GA20 promoted stem elongation in rosetted seedlings of Eustoma grandiflorum in the following order: GA1 = GA3 > GA20, whereas ent-kaurene (K), ent-kaurenoic acid (KA) and GA19 did not. GA1, GA3, GA19 and GA20 treatments promoted leaf elongation in the order of GA1 = GA3 = GA20 > GA19, although K and KA did not. Quantitative analysis of endogenous GAs suggested that GA-biosynthesis pathway prior to GA53 might be blocked in the rosetted plants. Furthermore, the results of stem and leaf elongation by the GA treatment indicate that there was a difference in 20-oxidase activity between stem and leaves of rosetted plants. Quantitative analyses also provided evidence that there were tissue-specific 20-oxidase activities not only in the rosetted plants but also in the non-rosetted plants of E. grandiflorum. GA3-induced stem elongation, but not floral initiation in rosetted plants under 35°/30°C. Uniconazole (UCZ) inhibited leaf expansion, stem elongation and flower bud development of the non-rosetted plants, but did not inhibit flower bud initiation. These results indicate that leaf expansion, stem elongation and flower bud development are apparently GA-dependent but flower bud initiation is not.